The present invention relates to an improved hot fillable plastic container having an improved side wall construction.
The packaging of certain liquids requires that they be packaged while hot. During filling the container is subjected to elevated temperatures, the container is capped and as the product cools a negative internal pressure or hot fill vacuum is formed within the container. The container construction for a plastic container must be able to withstand such internal pressure changes while maintaining the container configuration.
Various constructions have been proposed for plastic containers in an effort to maintain the integrity of the container during hot fill operations. Thus, the hot fill containers have been produced with a generally cylindrical main body which is provided with a plurality of elongated vertically oriented panels. These panels, which are commonly referred to as pressure or vacuum panels, are designed to collapse inwardly after the container has been filled with a hot liquid so as to accommodate the inevitable volume shrinkage of the liquid in the container as the liquid cools. However, the inward flexing of the panels caused by the hot fill vacuum creates high stress points at the top and bottom edges of the pressure panels, and especially at the upper and lower corners of the panels. These stress points weaken the portions of the side wall near the edges of the panels, allowing the side wall to collapse inwardly during handling of the container or when containers are stacked together.
Numerous design changes have been proposed to overcome this problem, including but not limited to design variations in the vacuum panels, axially extending posts between the vacuum panels and circumferential ridges above and below the vacuum panels. However, despite these numerous designs it has been found that collapse under vacuum still occurs, especially in localized areas.
It is, therefore, a principal objective of the present invention to provide an improved design for a hot fillable plastic container that resists vacuum collapse.
It is a further objective of the present invention to provide an improved hot fillable plastic container as aforesaid which has an aesthetically pleasing design and is cost effective.
It is a further objective of the present invention to provide an improved plastic container as aforesaid which maintains its structural rigidity under hot fill conditions in a simple design which is readily prepared on a commercial scale.
Further objects and advantages of the present invention will appear hereinbelow.